Here's why Jay Leno almost never uses credit cards

After the comedian's 22-year run hosting NBC's "The Tonight Show," he shifted gears and began hosting CNBC's "Jay Leno's Garage," a series that explores Americans' obsession with cars. Just last month, he launcheda car-care product line.

But Leno's massive success hasn't altered his financial philosophy, which has "always been really conservative," he tells CNBC.